The airfoil or wing surfaces of an aircraft are subject to the effects of transient atmospheric conditions posed by the weather systems of the winter season. The effects may manifest as frost, snow or ice, normally upon the upper and vertical surfaces of the aircraft skin. It is well known in the aircraft industry that such contamination of the wings has serious detrimental effects upon aircraft aerodynamics with the potential danger for loss of lift and control. An recent 1988 example of the tragic consequences of attempting flight with affected wing surfaces was unfortunately demonstrated in the Air Ontario crash of a Fokker F-28 at Dreyden, Ontario, Canada.
For some decades, protective covers have been provided to protect the surfaces of aircraft wings. Generally their use has been limited to light aircraft such as smaller, privately owned aircraft. An early example of such a device is disclosed in U.S. Pat. No. 3,044,516, issued to Stoll in 1962. This reference describes a wing covering device as an envelope-like receptacle for snugly fitting over a wing tip in a glove-like relation.
The commercial passenger aircraft industry uses large aircraft comprising narrow and wide body jets with typical wing spans of 100 feet and 200 feet respectively. Use of protective covers for this type of aircraft has been tried, but has not been commercially successful due in part to the size and installation difficulties. Such early covers were fabricated from heavy fabrics which absorbed water and tended to become unwieldy when wet. The cover could freeze into a stiff shape or worse, freeze to the wing surface.
Modern commercial aircraft surfaces are highly engineered components with surface finishes and structures which are particularly delicate and susceptible to damage and stresses other than those imposed by flight. Access for maintenance personnel to walk on the wing surfaces, for installation or removal of a cover, is now severely restricted and with the increased use of composite materials construction, walking loads are not allowed at all. Contact of the surfaces with metal fasteners, and the like, such as grommets disclosed by Stoll, is unacceptable. On many aircraft, delicate instruments and devices are mounted on the wing surfaces. These devices are fragile and must avoid mechanical damage. As an example of such a device, static wicks are located on the wing tips for discharging static during flight.
The airline industry is regulated under the auspices of the FAA in the United States, the MOT in Canada and similar agencies in other countries. These regulatory bodies require preventative de-icing and similar safety measures be performed for aircraft flight surfaces under certain weather conditions prior to takeoff. Presently, a typical treatment comprises applying a heated glycol solution to the wings. Generally, this is accomplished with a truck and boom arrangement whereby a water cannon directs a 160.degree. F. glycol solution onto the wings, removing snow, ice and frost with a combination of mechanical force and melting action. For smaller narrow body aircraft such as the McDonnell Douglas 80 (MD-80) or the Boeing 737, the amount of glycol used could be 20 to 200 US gallons per wing, dependent upon the level of contamination. A wide bodied aircraft such as the Boeing 747 could require up to 2000 US gallons per wing. The spent glycol flows to the tarmac surface where it can eventually cause damage to the concrete, or can pose a serious environmental impact if it reaches permeable ground. Glycol may be collected for recycling or an ash-like absorbent material is used to absorb the spent glycol and the waste is shipped to an industrial landfill. In some cases, the glycol is simply left on the tarmac with the attendant undesirable results.
The disadvantages to the glycol de-icing system include:
the significant cost of the glycol and procedures; PA1 serious delays and interruption of the airline departure schedule; and PA1 the environmental impact. PA1 That it was desirable to anchor the root or inner end of the cover to the fuselage with a loop or collar, as otherwise the wind could get between cover and wing and work the cover out toward the wing tip or twist it around one wing edge or the other; PA1 That it was necessary to form out-outs in the overhang portions so that the cover would have a form-fit around its protuberances located adjacent the wing edges, such as vortex generators, fairings, engine mounts and air dams. If this was not done and the cover was simply stretched or "tented" over the protuberance, air would enter through the openings created and would form frost and snow on the wing surface; PA1 That it was desirable to space the strap means less than 12 feet apart along the length of the panel, to enable two workers to efficiently install the cover. If the spacing was too great and conditions were windy, the workers had difficulty reaching back to a cinched portion to grasp the loose portion to cinch it at the next station; PA1 That it was necessary to form the panel of lightweight ultraviolet stabilized material which would not absorb water. A suitable material was found to be woven polyethylene, commonly used as lumber wrap. The woven nature of the material lends it the ability to resist propagation of tears--a useful feature in this application. However, this type of material was found to be relatively weak. It was liable to tear if the connecting straps were secured directly to the cover material and cinching stress was applied. It was therefore found desirable to form an anchoring "base" for the connecting straps. More particularly, the base comprised first and second lengths of webbing extending parallel and adjacent to the cover edge with one overlying the other, so that they sandwiched the cover between them. The anchor base further preferably comprised a third length of webbing extending laterally and inwardly from the first and second lengths, along the intended line of the cinching force. The cinching strap was secured to the T-shaped anchor so formed. PA1 a substantially wing-shaped panel having a root portion and leading and trailing edges, said panel being adapted to cover the upper surface of an airplane wing along part of its length, said panel having sufficient width so that a portion overhangs the leading edge of the wing and preferably overhangs both edges; PA1 The panel being formed of lightweight, ultraviolet-stabilized material which does not absorb any significant amount of water; PA1 The leading overhang portion being cut-out so as to form-fit around edge protuberances of the wing to be covered; and PA1 An array of strap means being positioned along the length of the cover in spaced-apart relation, for extending beneath the wing to secure the leading and trailing edges of the panel and to cinch the panel to the wing; PA1 said strap means being located at points spaced apart less than about 12 feet. PA1 (a) rolling the wing tip end of the panel toward its root portion to form a roll with the root portion free; PA1 (b) placing the roll onto the root area of the wing's upper surface, the roll being oriented transverse to the longitudinal projection of the wing, with the roll root portion directed toward the fuselage, whereby the roll may be unrolled toward the wing tip; PA1 (c) securing the roll root portion to the fuselage; PA1 (d) securing the roll root portion to the wing by connecting a first pair of associated strap members, respectively attached to the leading and trailing edges of the panel and extending beneath the wing, and cinching the panel edges together using the strap members to form-fit the roll root portion to the wing; PA1 (e) unrolling the panel away from the wing root and exposing a second panel portion and a second pair of associated strap members spaced from the first pair; PA1 (f) securing the panel second portion to the wing by connecting and cinching the second pair of associated strap members to form-fit the panel second portion to the wing; and PA1 (g) repeating the steps (e) and (f) of unrolling and securing the unrolled panel portions until the panel has been completely rolled out and covers the wing with a form-fit. PA1 rolling each of the tip portions toward the root portion to form a double-roll having first and second roll members; PA1 placing the double-roll onto the root portion of the wing surface, the double-roll being oriented transverse to the longitudinal projection of the wing and being centered on the fuselage axis, whereby the first and second roll members may be unrolled along the wing surface, in both directions toward the wing tips; and PA1 unrolling and securing the roll members as previously described with the low-wing version of the cover.
With this background in mind, it was the objective of the present invention to provide a wing cover, suitable for use with large aircraft, which could be easily installed and removed and which would result in reduced consumption of glycol.